Identification of an activation site in Bak and mitochondrial Bax triggered by antibodies.

ABSTRACT: During apoptosis, Bak and Bax are activated by BH3-only proteins binding to the ?2-?5 hydrophobic groove; Bax is also activated via a rear pocket. Here we report that antibodies can directly activate Bak and mitochondrial Bax by binding to the ?1-?2 loop. A monoclonal antibody (clone 7D10) binds close to ?1 in non-activated Bak to induce conformational change, oligomerization, and cytochrome c release. Anti-FLAG antibodies also activate Bak containing a FLAG epitope close to ?1. An antibody (clone 3C10) to the Bax ?1-?2 loop activates mitochondrial Bax, but blocks translocation of cytosolic Bax. Tethers within Bak show that 7D10 binding directly extricates ?1; a structural model of the 7D10 Fab bound to Bak reveals the formation of a cavity under ?1. Our identification of the ?1-?2 loop as an activation site in Bak paves the way to develop intrabodies or small molecules that directly and selectively regulate these proteins.

SUBMITTER: Iyer S 

PROVIDER: S-EPMC4890306 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature